Q.2 When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?

The deflection in the compass needle shows that the current is flowing through the wire and hence the current is flowing through the circuit.

Now when the free ends of a tester are dipped into a solution, the magnetic needle shows deflection.

That means the solution is certainly a conducting solution. And all the materials used in this case are conducting materials and thus the circuit becomes complete and the needle shows deflection.